About 150 registered nurses began a three-day strike at 7 a.m. Monday at a hospital and clinic in Hibbing, Minn. Medical care is continuing with about 40 temporary nurses, said officials of Fairview-owned Range Regional Health Services.

Both sides said no new talks are scheduled; nurses rejected a tentative agreement last month. They say their main issue is increasing the number and organization of nurses in the system.

"The nurses already are concerned for their patients. They're worried that current staffing is inadequate, and the new contract will put even more pressure on nurses to work when they're sick or too tired," said Jan Rabbers, a spokeswoman for the Minnesota Nurses Association, which represents the Hibbing nurses.

The nurses had threatened a brief strike in April, but pulled back as talks progressed. They are working under terms of their old contract, which expired Oct. 31.

The short-strike tactic was used in June 2010, when the Minnesota Nurses Association staged a one-day walkout at 14 Twin Cities hospitals.

Last month, the Hibbing nurses voted down a three-year offer that included a 1 percent pay raise in the second year and a 2.5 percent raise in the third year. It also would have set up a nurse-management committee to consider concerns about staffing levels, said Mitch Vincent, director of human resources.

"Now that is off the table," he said. "We're back to our February offer," which he said includes smaller pay increases and a less comprehensive staffing committee.

Contract talks with nurses also are underway at health systems in Bemidji, Grand Rapids, Ely and Virginia, and are scheduled to start next month in Thief River Falls.